Old Shotgun-Indentify

I was given this shotgun a few years ago. The elderly gentleman that gave it to me did not know much about it. I would like to repair refinish it. It appears to be about 20 Ga., though it is not marked. The barrel length is 29.5 inches. The letters TH are stamped on the top of each barrel about 1.5 inches from the breech. The bottom of the barrel under the forearm has some stampings: KRUPP-ESSEN FLUSSTAHL. There are also symbols stamped into the underside of the barrel, one looks similar to a dollar sign and the other an "S" with a crown or something above it. It is nicely engraved and has a monte carlo stock. This has some sloppy gunsmithing work done which I will need to correct. I will need to replace the rubber recoil pad with a steel plate. Also the plugs that hold the firing pins have been tack welded in place. Why might this have been done??? It appears that the gun will not function because the hammers do not strike the firing pins. It has a crisp trigger pull and the hammer falls sharply. When I remove the lock and look at the mechanism it appears that the hammer moves through its full range of motion. What could be keeping the hammers from striking??? Is a gun of this age safe for modern shells or should it just be a wallhanger?? I think that If I file away the welds, polish and reblue the reciever, the damage will not be noticable. I would appreciate any help with identification, locating parts or suggestions about how I might be able to repair it. Thanks, Scot